VERTEBRATE PALEONTOLOGY MATTHEW 287 



out and securing the first fruits of exploration — the evidence which 

 will confirm or disprove hypotheses and guesses that hitherto have 

 had free rein. 



SOME TRENDS OF MODERN WORK 



In the field of paleogeography I may call attention to three pub- 

 lications treating the subject from diverse or opposite viewpoints : 



Matthew : Climate and evolution, an essay of some 318 pages. 



Arldt : Paleogeographie, a treatise of 2 ponderous tomes. 



Case : Paleogeography of the Permian, a quarto volume of moder- 

 ate dimensions. 



It is commonly said that paleogeographie problems should be de- 

 cided only after marshaling all the evidence in every branch of 

 zoology, past and present, as well as of geology and physiography, 

 that can be brought to bear on it. This is what Doctor Arldt has 

 endeavored to do in his great treatise. I do not hold that view, for 

 it appears to me that unless evidence is thoroughly understood and 

 critically sifted as to its weight and its real significance, it is of no 

 value ; and it is obviously impossible for human intelligence to attain 

 a thoroughly critical grasp of so vast a field. On the other hand, the 

 evidence in any one branch, if interpreted rightly, will lead to cor- 

 rect conclusions, and if the conclusions drawn in one field conflict with 

 those drawn in another, it can only be because one or the other is 

 wrongly interpreted. It is not a question of balancing the evidence. 

 If it does not all point one way, then there is some mistake in the in- 

 terpretations placed on the facts. The problem then lies in finding 

 out what is the fallacy and in which field it lies, and whether the 

 evidence in several fields has been vitiated by the same fallacy. It 

 is only thus that one can arrive at true conclusions in problems of 

 this sort. To attempt to decide them by the balance of evidence, 

 as one would settle a problem in taxonomy, is more likely to put one 

 wrong than right. 



Doctor Case's volume is of interest as placing a novel and much 

 broader significance on the term paleogeography, making it almost 

 equivalent to what might be called paleoecology. He has little to 

 say in this volume as to the question of continental outlines, so com- 

 monly discussed as though it were the whole of the subject, but is con- 

 cerned chiefly with the habitat of the animals, its nature and changes, 

 and the physical geography of Permian North America. 



There has been for the past two decades a tendency among verte- 

 bratists to keep more closely in touch with stratigraphic geology. 

 The comparative anatomist, especially in setting forth the evolution 

 and specialization of structures, tends to arrange his material in 

 categories and sequences that show the evolution of structures and 

 organs, but are of course structural and not genetic sequences, as the 



